This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A119381 #12 Aug 04 2024 16:19:47 %S A119381 37,67,277,479,613,631,809,1297,1471,1607,1663,1721,1783,1867,1901, %T A119381 1931,1993,2137,2377,2411,2521,2683,2797,2879,3359,3571,3917,4391, %U A119381 4513,4621,5413,5437,5477,5647,6299,7321,7393,7873,7901,8087,8819,9007,10301 %N A119381 Primes p(n) for which (p(n-1) + p(n+2)) / p(n) = 2. %H A119381 Harvey P. Dale, <a href="/A119381/b119381.txt">Table of n, a(n) for n = 1..1000</a> %F A119381 a(n) = Prime(A119382(n)), where Prime(n) is the n-th prime. - _Stefan Steinerberger_, Jul 26 2006 %e A119381 In the ordered set of primes we have ...271,277,281,283... and (271+283)/277 = 2, therefore 277 belongs in this sequence. %t A119381 Prime[Select[Range[2, 1500], (Prime[ # - 1] + Prime[ # + 2])/(Prime[ # ]) == 2 &]] (* _Stefan Steinerberger_, Jul 26 2006 *) %t A119381 Select[Partition[Prime[Range[1300]],4,1],(#[[1]]+#[[4]])/#[[2]]==2&][[;;,2]] (* _Harvey P. Dale_, Aug 04 2024 *) %Y A119381 Cf. A119382. %Y A119381 Cf. A119382. %K A119381 easy,nonn %O A119381 1,1 %A A119381 _Axel Harvey_, Jul 25 2006 %E A119381 More terms from _Stefan Steinerberger_, Jul 26 2006